Natural gas, which is a naturally occurring material, contains water vapour as part of it's constituent make-up at the production temperature and pressure. This water vapour causes some operational problems in the production of natural gas and, as such, it must be removed from the natural gas. The removal of the water from the natural gas is called "dehydration" of the natural gas.
A common form of natural gas dehydration involves the use of glycol based liquids. These liquids, such as ethylene, diethylene or triethylene glycol, form a molecular bond with the water molecules in the natural gas. The glycol based liquids allow the water molecules to move from the gas phase to the glycol liquid phase thus dehydrating the natural gas. This process is most commonly done in a gas to liquid contractor.
The glycol which now contains water (called "rich glycol") must be processed to remove the water. This process of water removal from the rich glycol is called "reclamation" of the glycol. The glycol reclamation process involves the heating of the rich glycol to excite the water to glycol bond thus releasing the water molecule from the glycol molecule. The heating process occurs in a vessel called a "reboiler" and requires a significant amount of energy in the form of heat. The glycol, once free of water (called "lean glycol"), can be reintroduced into the dehydration process to collect more water from the natural gas.
The lean glycol, as it comes in contact with the natural gas, not only absorbs water molecules, but also absorbs other molecules that are naturally occurring in the natural gas. These other molecules, such as hydrocarbons (C1 to C10), carbon dioxide, benzene, toluene, ethyl benzene, xylene, hydrogen sulphide, mercaptans, and other sulphur compounds are also released from the glycol during the reclamation process. These other molecules released during the reclamation process are commonly called "fugitive emissions". It is common that these fugitive emissions are released directly to atmosphere. It is known that some of these fugitive emissions are toxic to humans, some are considered non-threshold carcinogens, and some are highly flammable. In order to avoid environmental contamination, steps are now being taken to direct fugitive emissions from glycol reclamation through a thermal oxidizer. Oxidization of the fugitive emissions is also requires a significant amount of energy in the form of heat.